The present invention relates generally to an improved method for fusion bonding a pair of thermoplastic articles, which includes the conventional steps of bringing each surface to be bonded into physical engagement and contact with the surface portion of a heated platen, and thereafter maintaining such engagement until the surfaces of the thermoplastic articles become fused. Upon reaching fusion in the areas to be bonded, the articles are transferred into face-to-face relationship until the fused surfaces become solidified. In addition to these steps in the operation, the additional step is added which includes abrading the contact surfaces of the platen to renew and expose the metallic surface thereof for engagement with the surface of the next thermoplastic article to be treated.
Fusion bonding of certain low and medium melting point thermoplastic articles has been undertaken in the past, and is presently widely utilized for the formation of certain articles consisting of thermoplastic materials. Such methods have been successfully utilized in connection with relatively low melting thermoplastic materials such as polyethylene, polypropylene, polystyrene, and the like. With certain higher melting thermoplastic materials such as nylon, specifically crystalline nylon, fluorinated hydrocarbons such as Halar, are not considered as candidates for fusion bonding, particularly when contact with a heated platen is considered. Non-contact heating may be undertaken, but this procedure requires exceptionally long cycle times and is generally regarded as being unsatisfactory for production of most articles fabricated of such materials. It has been found, in accordance with the present invention, that fusion bonding of high melting point thermoplastic articles including nylon and florinated hydrocarbons is possible utilizing contact heating, with the present invention including the additional step of abrading the contact surfaces of the platen to renew and expose the metallic surfaces thereof prior to engagement with the surface of each thermoplastic article being treated. The abrading operation is conveniently accomplished by exposing the surfaces of the platen to wire bristle brushes, and preferably rotating wire brushes of cylindrical configuration during a portion of an operating cycle.